Okaye Gordon, 30, had been living on the mountain in a makeshift encampment where police found him in a tent burning a fire pit, according to police.
Belmont police had hiked up the mountain at about 10 a.m. Thursday responding to reports of an open fire pit burning embers.
Gordon was arrested on an outstanding warrant for assault, according to police. He was brought to a hospital to be treated for smoke inhalation and dehydration.
Belmont and San Mateo firefighters were called to the scene and extinguished the pit within minutes, a fire official said.
The San Mateo Fire Department has units designed to put out fires in wilderness areas.